/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.common.networking;

import net.sf.freecol.common.model.Ability;
import net.sf.freecol.common.model.Europe;
import net.sf.freecol.common.model.Europe.MigrationType;
import net.sf.freecol.common.model.Game;
import net.sf.freecol.common.model.Player;
import net.sf.freecol.server.FreeColServer;
import net.sf.freecol.server.model.ServerPlayer;

import org.w3c.dom.Element;


/**
 * The message sent when a unit is to emigrate.
 */
public class EmigrateUnitMessage extends DOMMessage
{

    /** The slot from which to select the unit. */
    private final String slotString;


    /**
     * Create a new <code>EmigrateUnitMessage</code> with the supplied slot.
     *
     * @param slot The slot to select the migrant from.
     */
    public EmigrateUnitMessage( int slot )
    {
        super( getXMLElementTagName( ) );

        this.slotString = Integer.toString( slot );
    }

    /**
     * Create a new <code>EmigrateUnitMessage</code> from a supplied element.
     *
     * @param game The <code>Game</code> this message belongs to.
     * @param element The <code>Element</code> to use to create the message.
     */
    public EmigrateUnitMessage( Game game, Element element )
    {
        super( getXMLElementTagName( ) );

        this.slotString = element.getAttribute( "slot" );
    }


    /**
     * Handle a "emigrateUnit"-message.
     *
     * @param server The <code>FreeColServer</code> handling the message.
     * @param player The <code>Player</code> the message applies to.
     * @param connection The <code>Connection</code> message was received on.
     * @return An <code>Element</code> encapsulating the change,
     *         or an error <code>Element</code> on failure.
     */
    public Element handle( FreeColServer server, Player player,
                           Connection connection )
    {
        final ServerPlayer serverPlayer = server.getPlayer( connection );

        Europe europe = player.getEurope( );
        if ( europe == null )
        {
            return DOMMessage.clientError( "No Europe to migrate from." );
        }
        int slot;
        try
        {
            slot = Integer.parseInt( slotString );
        }
        catch ( NumberFormatException e )
        {
            return DOMMessage.clientError( "Bad slot: " + slotString );
        }
        if ( ! MigrationType.validMigrantSlot( slot ) )
        {
            return DOMMessage.clientError( "Invalid slot for recruitment: "
                                                   + slot );
        }

        MigrationType type;
        if ( serverPlayer.getRemainingEmigrants( ) > 0 )
        {
            if ( MigrationType.unspecificMigrantSlot( slot ) )
            {
                return DOMMessage.clientError( "Specific slot expected for FoY migration." );
            }
            type = MigrationType.FOUNTAIN;
        }
        else if ( player.checkEmigrate( ) )
        {
            if ( MigrationType.specificMigrantSlot( slot )
                    && ! player.hasAbility( Ability.SELECT_RECRUIT ) )
            {
                return DOMMessage.clientError( "selectRecruit ability absent." );
            }
            type = MigrationType.NORMAL;
        }
        else
        {
            if ( ! player.checkGold( europe.getRecruitPrice( ) ) )
            {
                return DOMMessage.clientError( "No migrants available at cost "
                                                       + europe.getRecruitPrice( )
                                                       + " for player with " + player.getGold( ) + " gold." );
            }
            type = MigrationType.RECRUIT;
        }

        // Proceed to emigrate.
        return server.getInGameController( )
                .emigrate( serverPlayer, slot, type );
    }

    /**
     * Convert this EmigrateUnitMessage to XML.
     *
     * @return The XML representation of this message.
     */
    @Override
    public Element toXMLElement( )
    {
        return createMessage( getXMLElementTagName( ),
                              "slot", slotString );
    }

    /**
     * The tag name of the root element representing this object.
     *
     * @return "emigrateUnit".
     */
    public static String getXMLElementTagName( )
    {
        return "emigrateUnit";
    }
}
